Enlarging bore holes by pellet drilling



Nov. 20, 1956 J. E. ECKEL ET AL 2,771,269

ENLARGING BORE HOLES BY PELLET DRILLING 2 Sheets-Sheet 1 Filed June 50. 1953 REANED 0R ENLARGED HOLE- FlG.-|

DEFLECTOR TAPER (HARD SURFAOED) LOCATER SHOULDER ORIGINAL HOLE DIAMETER PILOT BAR Nov. 20, 1956 J. E. ECKEL ETAL 2,771,269

ENLARGING BORE HOLES BY PELLETDRILLING 2 Sheets-Sheet 2 Filed June 50, 1953 E L 0 H D E G R A L N E R 0 D E M A E R F' l G. 2

SUPPORT BARS LOCATER SHOULDER ORIGINAL HOLE DIAMETER R A B T 0 IL P INVENTORS- JOHN E. ECKEL. FRANK G. BQUCJ-IER monutv Unite Sttes Patent ENLARGIN G BORE HOLES BY PELLET DRILLING John E. Eckel and Frank G. Boucher, Tulsa, Okla., as-

signors to Esso Research and Engineering Company, a corporation of Delaware Application June 30, 1953, Serial No. 365,096

3 Claims. (Cl. 2551.8)

The present invention is concerned with a novel method and apparatus for enlarging the diameter of a previously drilled bore hole. The invention utilizes what is known as pellet impact drilling.

It is often desirable to increase the diameter of a bore hole that has already been drilled in the earth. For example, in the drilling of oil wells it is frequent practice to drill ahead of the normal sized hole to obtain cores for geological inspection and it is then later necessary to enlarge the hole to full gauge as drilling progresses. Also it is common practice to drill a rat hole ahead of a full gauge hole for the purpose of supporting a drill stem tester in the bore hole. After the test has been run, it is then necessary to drill the hole to full gauge. With conventional reaming bits that are used for the bore hole enlarging operation it often happens that the reaming bit teeth become dulled before the full length of the hole has been reamed, which necessitates removing the drill string and replacing the reaming bit. With a drill bit utilizing the pellet impact principle this would not be necessary since all that would be required would be to supply additional pellets as the original pellets are worn down or lost.

The basic principles of the pellet impact technique for the drilling of bore holes involve the use of a stream of fluid pumped from the surface of the earth through a tubular member to a jet nozzle assembly adjacent the bottom of the bore hole. The jet nozzle assembly is adapted to direct a high velocity jet of fluid against the formation being drilled and is provided with means for entraining in the jetted fluid a multitude of pellets which are accelerated to high velocity in the jet stream and thereby acquire considerable kinetic energy so that when the pellets impinge against the formation the resulting percussive and fracturing forces exert a drilling action. Preferably the pellets that are employed are smooth, nonabrasive and essentially spherical and are of substantial size, preferably in the size range of about /s" to about 1" in diameter. It is preferred that hard, tough metallic alloys be employed as the pellet material. The basic principles of the technique of drilling by pellet impact are set forth in co-pending application Ser. No. 268,873, filed by Philip S. Williams, on January 29, 1952 and entitled Pellet Impact Drilling Method and Apparatus.

The present invention is directed to the use of the pellet impact technique for enlarging the diameter of a bore hole. A fluid jet issuing from a primary nozzle is directed into a tubular mixing chamber, also referred to as a secondary nozzle, wherein pellets are entrained in the fluid jet and the jetted fluid and pellets are discharged from the lower end of the chamber or nozzle. The stream of pellets and fluid leaving the secondary nozzle is directed so that the pellets will impinge on the side of the bore hole and thereby enlarge the same. This is done either by directing the stream against a sloping deflector guide or by positioning the secondary nozzle at a desired angle from the vertical. An elongated pilot guide bar or plug member of essentially the same 2,77 1,269 Patented Nov. 20, 1956 diameter as the original hole is supported below the tubular chamber or secondary nozzle and serves to center the device in the bore hole as well as to prevent the loss of pellets down through the original bore hole. A locator shoulder on the guide bar or pilot member rests on the ledge created at the bottom of the enlarged hole and thus controls the position of the drill with respect to the portion of the formation that is being drilled.

A fuller understanding of the nature of this invention may be obtained by reference to the accompanying drawing in which:

Figure l is an elevational view in section showing one embodiment of the invention in position in a bore hole; and

Figure 2 is a similar elevational view, partly in section, showing a second embodiment of the invention in position in a bore hole.

Referring now to Figure 1 in particular, a bore hole 10 is shown which it is desired to enlarge so as to obtain a bore hole 11 having a greater diameter than the original bore hole. A drilling apparatus of a character to accomplish this objective in accordance with the present invention is shown in reaming position. The apparatus is supported in the bore hole on a tubular support 12 which is adapted for attachment to the lower end of a conventional drill pipe. The lower end of member 12 terminates in a nozzle element 13. Supported below the tubular member 12 and attached thereto by suitable means such as the web supporting members 14 shown is a second tubular element 15 which is positioned in substantial alignment with the primary nozzle. Fluid access to the top of the second tubular element from the bore hole annulus is provided through the throat or opening 21.

Positioned below element 15 and fastened thereto by suitable means such as support member 20 is a pilot bar or closed plug element 16 which is constructed to have a diameter substantially that of the bore hole 10 that is to be reamed. The pilot bar serves the dual purpose of preventing the loss of pellets down the original bore hole as Well as centering the device in the bore hole. The top of the pilot bar 16 presents an inclined deflector surface 17 so that the fluid and pellets leaving the bottom of the second tubular element will be deflected laterally to impinge against the wall of the bore hole to enlarge the same, as shown. Pilot bar 16 is provided with an outwardly extending shoulder 18 which rests at the bottom 23 of the enlarged bore hole so as to position the apparatus properly with respect to the portions of the formation that are being drilled.

To conduct the desired bore hole enlarging operation the apparatus illustrated is inserted in the bore hole until the pilot bar or plug element 16 enters the smaller diameter portion of the bore hole 10 and the shoulder 18 comes to rest at the bottom of the larger bore hole 11. Then a plurality of pellets are placed in the bore hole. These will come to rest at the bottom of the larger bore hole and will be prevented from falling into the smaller portion of the bore hole by the pilot bar or plug element. Fluid is then pumped down the drill pipe through nozzle 13. As it leaves this nozzle the fluid is converted into a high velocity jet stream which then enters tubular element or secondary nozzle 15 and passes through the same to impinge on the deflector surface 17 which directs the stream laterally against the side of the bore hole. The circulating fluid returns up the bore hole annulus and carries with it some of the pellets lying at the bottom of the enlarged portion of the bore hole. Essentially no fluid will be lost past the plug element 16 since the smaller bore hole 10 will be filled with fluid from previous operations. As the upward flowing stream of pellets and fluid reaches the enlarged annulus that exists above the top of the secondary nozzle 15 the velocity ofthestream-is reducedso-thatthe-pellets tend to accumulate in this area and will be drawn into the throat of the secondary nozzle 15 by gravity action as well as by the aspiration effect createdb'y passage-of the fluid'jet from the primary nozzle into the secondary nozzle. The pellets that enter tubular element ornoz zle 15 will be admixed with the high velocity jet of'fluid and will attain substantially the same velocity as the the stream of pellets and fluid will be directed-inevery' direction about the bore hole so as to drill the same uniformly.

Asecond embodiment-of the invention is shown in elevation in Figure 2. In this embodiment the pilot bar or plug member 16 is supportedby the tubular member 12 by means of one or more support bars 24. The second tubular element or secondary nozzle 25, which is shown partially sectioned along its length, is welded to the top of the guide bar 16 and is positioned at an angle from the vertical so as to direct the stream of pellets and fluid in a lateral direction to'drill, as shown, an enlarged hole by direct impingement of the pellets carried by the jet stream. The lower termination30 of the primary nozzle 13 is directed at substantially the same angle as the secondary nozzle 25'so as to be essentially coaxial therewith. As in the embodiment of Figure 1 the rotating shoulder 28 fastened to pilot bar 16 positions the drill at the proper level'in the bore hole'so as to effect the desired drilling operation.

Each of the embodiments shown has some advantages over the other. For example that of Fig. l is simpler to construct and provides for more efliecient recycling of pellets. The embodiment shown in Fig. 2 has the advantage of more eflicient use of the kinetic energy supplied to the pellets in view of the fact that the pellets impinge directly against the formation without first losing some energy to a deflector surface. stood that the embodiments shown and described have been presented by way of example and that the inventionis not to be limited thereto. The true scope of the invention is defined in the appended claims.

What is claimed is:

l. A drilling apparatus for enlarging the diameter of a bore hole in the earth comprising a tubular support member terminating at its lower end in a jet nozzle adapted to provide a downwardly directed high velocity- It is to be under' stantially aligned with said jet nozzle, a plug element supfrom the bore hole annulus, said plug member having an inclined upper" surface" whereby "to" deflect laterally fluids and solids impinging thereon from said second tubular member, said plug element having a diameter substantially that of the bore hole to be enlarged, and a lateral projection adjacent the upper end of said plug element whereby to position the same atthe bottom of the enlarged portion of the bore hole.

2. A drilling apparatus for enlarging the diameter of a bore hole in the earth comprising a tubular support member terminating at its lower end in a jet nozzle adapted to provide a downwardly directed high velocity jet of fluid, a second tubular member positioned below said jet nozzle and supported by saidfirst tubular member with the inner bore. of said second tubular member substantially aligned with said jet nozzle, said second tubular member having its lower end directed in a downward direction away from the bore hole axis whereby to direct fluids and solids emerging from said tubular member against the bore hole wall, a plug element fastened to and extending below saidsecond'tubular'member, said' plug element having a diameter substantially that'of th e bore hole to be enlarged, and a lateral projection adjacent the upper. end of said'plug-element whereby to position the same adjacent the bottom of the enlarged portion of the bore hole.

3. The method of enlarging the-diameterof a bore hole in the earth comprising the steps of directing a high velocity jet of fluid downwardly in thebore hole, introducing-into and admixingvwith saidjet a plurality of essentially spherical pellets of substantial size, directing said mixture against the walls of the bore hole in a generally downward direction whereby said-pellets are impinged against said wall to drill an enlarged'annulus, conducting said fluid and pellets upwardly in said enlargedannulus, removing said pellets from said upflowing fluid, reintroducing said pellets into said fluid jet," continuously blocking entry of pellets into the original bore hole below said enlarged annulus by positioning: blockingv means in said original bore hole in the vicinity of the bottom of said enlarged annulus and gauging the proper positioning of said *bl'ockingjmeans by continuallyresting an upper lateral' projection thereof on saidbottom of said enlarged annulus.

References Citedin'the' file of this patent UNITED STATES PATENTS 1,869,843 Cole -Aug; 2,- 1932 2,072,627 Zublin Mar. 2-, 1937 2,233,260 Hawthorne Feb. 25, 1941 2,312,018 Beckman Feb. 23, 1943" FOREIGN PATENTS 230,078 Great Britain July 23, 1925 

